Battery cell of curved shape and battery pack employed with the same

ABSTRACT

Disclosed herein is a battery cell configured such that an electrode assembly of a cathode/separator/anode stack structure is mounted in a changeable cell case in a state in which the electrode assembly is impregnated with an electrolyte, wherein the electrode assembly and the cell case are curved in the same direction on axial vertical sections thereof in a state in which opposite ends of the electrode assembly and opposite ends of the cell case are directed in the same direction about a middle part of the electrode assembly and a middle part of the cell case. When the battery cell is mounted in an electronic device the external shape of which is curved or in an electronic device configured such that a battery mounting region thereof is curved, the tight contact between the battery cell and the electronic device is achieved, thereby maximizing space utilization and thus providing high efficiency. Also, electronic devices having aesthetically pleasing appearance and various designs satisfying liking of consumers are developed using the battery cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 12/922,005 filed on Jan. 11, 2011, which is a National Stage ofPCT/KR2009/001189 filed on Mar. 10, 2009, which claims priority toKorean Application No. 10-2008-0023054 filed on Mar. 12, 2008. Theentire contents of all of the above applications are hereby incorporatedby reference.

TECHNICAL FIELD

The present invention relates to a curved battery cell and a batterypack including the same, and, more particularly, to a battery cellconfigured such that an electrode assembly of a cathode/separator/anodestack structure is mounted in a changeable cell case in a state in whichthe electrode assembly is impregnated with an electrolyte, wherein theelectrode assembly and the cell case are curved in the same direction onaxial vertical sections thereof in a state in which opposite ends of theelectrode assembly and opposite ends of the cell case are directed inthe same direction about a middle part of the electrode assembly and amiddle part of the cell case.

BACKGROUND ART

As mobile devices have been increasingly developed, and the demand forsuch mobile devices has increased, the demand for secondary batterieshas also sharply increased as an energy source for the mobile devices.Among such secondary batteries is a lithium secondary battery havinghigh energy density and high discharge voltage, on which much researchhas been carried out and which is now commercialized and widely used.

In terms of the shape of batteries, the demand for prismatic secondarybatteries or pouch-shaped secondary batteries, which are thin enough tobe applied to products, such as mobile phones, is very high. In terms ofthe material for batteries, the demand for lithium secondary batteries,such as lithium ion batteries and lithium ion polymer batteries, havinghigh energy density, high discharge voltage, and high power stability,is very high.

The size and thickness of electronic devices have been increasinglyreduced so as to satisfy liking of consumers. For this reason, thereduction in size and thickness of secondary batteries is also requiredso as to maximize space utilization. Therefore, it is necessary toprovide various shapes of the secondary batteries corresponding to theshapes of the electronic devices and, in addition, to efficientlyutilize the internal space of each of the electronic devices.

In particular, in recent years, designs of the electronic devices haveplayed a very important role when consumers choose the electronicdevices. For this reason, various designs are provided in place of aflat type design. For example, electronic devices, such as mobile phonesand laptop computers, may be designed such that the electronic devicescan be curved in an ergonomic manner.

A plurality of curved electronic devices has been developed andcommercialized; however, most of the manufactured batteries areconfigured in a flat shape. As a result, space utilization is low, andit is difficult to mount batteries in the respective electronic devicesdue to such low space utilization. When external impact is applied tothe electronic devices, therefore, the batteries may freely move in therespective electronic devices, with the result that the batteries may bedamaged.

In order to mount a battery in an electronic device configured such thata battery mounting region, in which the battery will be mounted, iscurved, therefore, it is required to curve the battery such that thebattery is stably mounted in the curved battery mounting region of theelectronic device.

Some technology for curving an electrode assembly has been proposed. Forexample, US Patent Application Publication No. 2007/0059595 disclosed abattery having a jelly-roll type electrode assembly configured such thata section of the electrode assembly perpendicular to a winding axis iscurved. According to this disclosure, the curve is formed throughthermal pressing using a concave heater and a convex heater.

Also, Japanese Patent Application Publication No. 1999-307130 disclosesa method of thermally pressing a stack type electrode assembly using tworolls having different diameters to manufacture a battery configured ina curved structure.

According to the above disclosures, however, the electrode assembly isdirectly thermally pressed, with the result that deterioration of thebattery occurs, which is very serious. In addition, the formertechnology is applied to the winding type electrode assembly(jelly-roll), with the result that larger stress occurs at the middlepart of the electrode assembly on which stress is concentrated, andtherefore, shape deformation, such as twisting, of the electrodeassembly is great. On the other hand, the latter technology is appliedto the stack type electrode assembly, with the result that, when theelectrode assembly is pressed using the heating rolls, some electrodeplates are nonuniformly pushed due to shear stress, and therefore, ashort circuit may occur at opposite ends of the electrode assembly.

Furthermore, the above technology curves the electrode assembly, andtherefore, it is necessary to curve a battery case in the same manner.Also, when an electrolyte is injected in to the battery case in a statein which the curved electrode assembly is mounted in the battery case,stress immanent in the electrode assembly during curving the electrodeassembly is restored by a plasticizing action of the electrolyte, andtherefore, the ends of the electrode assembly are pressed by the insideof the battery case, with the result that a possibility of a shortcircuit is increased.

Therefore, there is a high necessity for a secondary battery (batterycell) which is gently curved in the axial direction thereof, therebysolving the above-mentioned problems.

DISCLOSURE Technical Problem

Therefore, the present invention has been made to solve the aboveproblems, and other technical problems that have yet to be resolved.

As a result of a variety of extensive and intensive studies andexperiments to solve the problems as described above, the inventors ofthe present application have found that when a battery cell, having achangeable cell case and configured such that the battery cell curved onthe axial vertical section thereof in a state in which the opposite endsof the battery cell are directed in the same direction about the middlepart of the battery cell, is mounted in an electronic device theexternal shape of which is curved, it is possible to maximize spaceutilization, to develop electronic devices having various designssatisfying liking of consumers, and to solving the above-mentionedproblems, such as a short circuit. The present invention has beencompleted based on these findings.

Technical Solution

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a battery cellconfigured such that an electrode assembly of a cathode/separator/anodestack structure is mounted in a changeable cell case in a state in whichthe electrode assembly is impregnated with an electrolyte, wherein theelectrode assembly and the cell case are curved in the same direction onaxial vertical sections thereof in a state in which opposite ends of theelectrode assembly and opposite ends of the cell case are directed inthe same direction about a middle part of the electrode assembly and amiddle part of the cell case.

Consequently, when the battery cell according to the present invention,which is curved in the axial direction thereof, is mounted in anelectronic device the external shape of which is curved or in anelectronic device the external shape of which is flat but which isconfigured such that a battery mounting region thereof is curved, thetight contact between the battery cell and the electronic device isachieved, thereby maximizing space utilization and thus providing highefficiency. Also, it is possible to develop electronic devices havingvarious designs satisfying liking of consumers.

For example, a stack type or folding type electrode assembly may be usedas the electrode assembly of the battery cell according to the presentinvention. In a simple stack type electrode assembly, however, someelectrode plates are pushed during curving of the electrode assemblywhen interface friction between the electrode plates is not uniform, andtherefore, the electrode plates contact each other at the ends of theelectrode assembly, with the result that a short circuit may occur. Inthe folding type electrode assembly, on the other hand, large shapedeformation, such as twisting, of the electrode assembly may occur atthe middle part of the electrode assembly on which stress isconcentrated, and the electrode assembly can be curved only in thewinding direction thereof.

In a preferred example, the electrode assembly may be configured in astack/folding type structure in which stack type bi cells or full-cells,as unit cells, are sequentially wound in a state in which a longseparation sheet is disposed between the bi-cells or the full-cells. Insuch a stack/folding type electrode assembly, opposite ends of theelectrode assembly are sealed by the separation sheet, and, the stackedstate of the electrode plates is maintained by the winding force of theseparation sheet even when the interface friction between the electrodeplates is not uniform, and therefore, it is possible to prevent theoccurrence of a short circuit as described above.

Details of the stack/folding type electrode assembly are disclosed inKorean Patent Application Publication No. 2001-0082058, No.2001-0082059, and No. 2001-0082060, which has been published in the nameof the applicant of the present application. The disclosures of theabove-mentioned patent application publications are hereby incorporatedby reference as if fully set forth therein.

According to the present invention, the cell case is changeable suchthat the cell case can be easily curved in a state in which theelectrode assembly is mounted in the cell case. That is, the changeablecell case may be deformed by external force in a state in which theelectrode assembly is mounted in the cell case. Preferably, thechangeable cell case may be a pouch-shaped case formed of a laminatesheet including a metal layer and a resin layer. Preferably, therefore,the battery cell is configured in a structure in which the outercircumference of the pouch-shaped case is sealed by thermal welding in astate in which the electrode assembly is mounted in the pouch-shapedcase.

The laminate sheet may be configured such that an outer resin layerexhibiting high durability is attached to one surface (outer surface) ofa metal blocking layer, and a resin sealant layer exhibiting highthermal weldability is attached to the other surface (inner surface) ofthe metal blocking layer.

The outer resin layer must have high tolerance to external environment,and it is necessary for the outer resin layer to have predeterminedtensile strength and corrosion resistance. To this end, the outer resinlayer may be made of a polymer resin, such as polyethylene terephthalate(PET) or oriented nylon film.

It is required for the metal blocking layer to prevent introduction orleakage of foreign matter, such as gas or moisture, into or from thebattery cell and to improve strength of the cell case. Preferably, themetal blocking layer is made of aluminum.

The resin sealant layer is made of a polymer resin which exhibits highthermal weldability (thermal adhesive property) and a low hygroscopicproperty, which is necessary to restrain permeation of the electrolyte,and is not expanded or is not corroded by the electrolyte, such aspolyolefin, more preferably cast polypropylene (CPP).

Generally, polyolefin, particularly polypropylene, has low adhesion withmetal. For this reason, an adhesion layer may be further disposedbetween the resin sealant layer and the metal blocking layer so as toimprove adhesion between the resin sealant layer and the metal blockinglayer. The adhesion layer may be made of, for example, urethane, acryl,or thermoplastic elastomer, to which, however, the material for theadhesion layer is not limited.

As previously described, the battery cell according to the presentinvention is gently curved on the axial vertical section thereof suchthat the opposite ends of the battery cell are directed in the samedirection about the middle part of the battery cell. Here, that thebattery cell is curved such that the opposite ends of the battery cellare directed in the same direction means that the battery cell is curvedsuch that both the opposite ends of the battery cell are directed upwardor downward.

In the battery cell according to the present invention, the electrodeterminals may be provided at only one of the curved opposite ends of theelectrode assembly. Alternatively, the electrode terminals may beprovided at both the curved opposite ends of the electrode assembly.However, the electrode terminals may be disposed in different manners.

The electrode assembly and the cell case may be curved such that theelectrode assembly and the cell case have a radius of curvature R of 50Rto 150R.

That is, the radius of curvature R of the electrode assembly and thecell case may be variously adjusted based on desired shapes. However, ifthe radius of curvature is too small, stress is concentrated on themiddle part of the battery cell, with the result that the battery cellmay be twisted. On the other hand, if the radius of curvature is toolarge, it is difficult to control the radius of curvature, and theelectrode assembly and the cell case may return to original statesthereof, that is, flat states, which is not preferable.

Generally, when a plurality of plate-shaped stacked members are curvedsuch that the stacked members have a predetermined radius of curvature,the inner stacked members have a greater strain than the outer stackedmembers. During charge and discharge of the secondary battery, on theother hand, active materials applied to the electrode plates repeatedlyexpand and contract. As a result, it is difficult to maintain thebattery cell in a predetermined curved state. In a secondary batteryhaving a small radius of curvature, i.e., a secondary battery which isgreatly curved, therefore, the curved state of the secondary battery maybe restored during repetitive charge and discharge of the secondarybattery. In this case, the ends of the respective electrode plates arepressed by the cell case, with the result that large force is applied tothe electrode plates, and the electrode plates penetrate the separators.Consequently, a short circuit may occur.

In a preferred example, therefore, the curved opposite ends of theelectrode assembly and the cell case may have a radius of curvature R₁greater than a radius of curvature R₂ of the middle parts of electrodeassembly and the cell case. Specifically, the above structure isconfigured such that, when the electrode assembly and the cell case arecurved to have an average radius of curvature R, the radius of curvatureR₂ of the middle parts of the electrode assembly and the cell case isless than the average radius of curvature R, and the radius of curvatureR₁ of each end of the electrode assembly and the cell case is greaterthan the average radius of curvature R.

In the above structure, a strain due to restoration at the opposite endsof the electrode assembly and the cell case having the large radius ofcurvature R₂ is less than a strain due to restoration at the oppositeends of the electrode assembly and the cell case a radius of curvatureR₁ in the same condition, and therefore, when the active materialsapplied to the electrode plates repeatedly expand and contract duringrepetitive charge and discharge of the secondary battery, force appliedto the ends of the electrode assembly is small, and therefore, it ispossible to greatly reduce a possibility of the occurrence of a shortcircuit as previously described.

Also, when the electrode terminals are provided at only one of thecurved opposite ends of the electrode assembly or at both the curvedopposite ends of the electrode assembly, the electrode terminals arelocated along the curved ends of the electrode assembly, with the resultthat the coupling between the electrode terminals and a cap plate, suchas a protection circuit module (PCM), is not easily achieved. However,when the radius of curvature R₁ of the opposite ends of the electrodeassembly and the cell case is relatively large, a relatively gentlecurve is provided, with the result that the curved angle of theelectrode terminals is decreased, and therefore, it is possible tostably achieve the coupling between the electrode terminals and the capplate.

The radius of curvature R₁ of the opposite ends of the electrodeassembly and the cell case and the radius of curvature R₂ of the middleparts of electrode assembly and the cell case may be appropriatelyadjusted within a range to minimize a possibility of the occurrence of ashort circuit as previously described. It is not necessary to provide agreat difference between the radius of curvature R₁ of the opposite endsof the electrode assembly and the cell case and the radius of curvatureR₂ of the middle parts of electrode assembly and the cell case.Preferably, the radius of curvature R₁ is 51R to 180R in a condition inwhich radius of curvature R₁ is greater than the radius of curvature R₂,and the radius of curvature R₂ is 50R to 150R.

In accordance with another aspect of the present invention, there isprovided a manufacturing method of a curved battery cell having a radiusof curvature R, the manufacturing method including (a) mounting anelectrode assembly in a changeable battery cell, injecting anelectrolyte into the cell case, sealing the battery cell so as tomanufacture an upright battery cell, and initially charging anddischarging the upright battery cell, (b) placing the upright batterycell between upper and lower jigs having a radius of curvature r lessthan the radius of curvature R and moving the upper and lower jigstoward to each other to press the upright battery cell, and (c)separating the upper and lower jigs toward from each other to remove thebattery cell from the upper and lower jigs and leaving the battery cellalone for a predetermined time such that a curved state of the batterycell is partially restored, and therefore, the battery cell has theradius of curvature R.

As previously described, the conventional technology for directlycurving the electrode assembly or the electrode plates has beenproposed. In the conventional technology, however, severe shapedeformation of the electrode assembly occurs due to expansion andcontraction of the electrode plates during initial charge and dischargeof the battery cell carried out after the injection of the electrolyteinto the cell case. In the manufacturing method of the battery cellaccording to the present invention, on the other hand, only theelectrode assembly is not curved, but the electrode assembly is mountedin the cell case, the electrolyte is injected into the cell case,initial charge and discharge of the resulting battery cell is performed,and the battery cell is curved at a post process. Consequently,deformation is relatively small, and heat is not directly applied to theelectrode assembly, with the result that deterioration of the electrodeassembly is minimized.

Also, in a case in which the electrode assembly is pressed such that theelectrode assembly is curved, it is necessary to curve the cell case, inwhich the electrode assembly will be mounted. However, such a curvingprocess is not easily performed, and the overall process is complicated.According to the present invention, on the other hand, the cell case ispressed together with the electrode assembly such that both the cellcase and the electrode assembly can be simultaneously curved, andtherefore, process efficiency is excellent.

In addition, the electrolyte in the cell case serves as a kind ofplasticizer to minimize stress caused due to interface friction betweenthe electrode plates during the execution of the pressing process, andtherefore, it is possible to greatly reduce restoration of the curvedbattery cell due to such stress during repetitive charge and dischargeof the battery cell.

In order to easily achieve such simultaneous curving, the cell case maybe made of a changeable material that can be easily deformed and curvedduring the execution of the step (b) of pressing the battery cell.

The step (b) of pressing the battery cell is carried out to curve theoutside of the battery cell. In this step, the battery cell is pressedusing a jig (for example, a concave jig) having a shape corresponding toa desired curve of the battery cell and a jig (for example, a convexjig) having a shape corresponding to the shape of the concave jig.

According to circumstances, heat treatment may be carried out during thestep of pressing the battery cell. In this case, heat treatment methodsare not particularly restricted. For example, a heater may be mounted inat least one of the jigs such that the battery cell can be heated whilebeing pressed.

Pressure and temperature which is applied to the battery cell during thestep of pressing the battery cell is sufficient not to causedeterioration of the electrode assembly in the battery cell. Preferably,the step of pressing the battery cell is carried out at a pressure of150 to 500 kgF and a temperature of 10 to 90° C. More preferably, thestep of pressing the battery cell is carried out at a room pressurewithout heating.

In the step (c) of leaving the battery cell alone, stress generated inthe battery cell during the execution of the step of pressing thebattery cell is released to stably maintain the curved shape of thebattery cell such that the battery cell has the predetermined radius ofcurvature R.

In accordance with a further aspect of the present invention, there isprovided a battery pack configured such that the curved battery cell asdescribed above is mounted in a pack case curved in the same shape asthe battery cell.

Preferably, the battery pack is used as a power source for mobilephones. Generally, mobile phones are configured in a rectangular shape,and a battery is mounted in the lower end of each of the mobile phones.Preferably, mobile phones are designed such that a voice reception partand a voice transmission part of each of the mobile phones are locatedat positions corresponding to an ear and mouth of a user or near suchpositions. To this end, in a case in which the curved battery cellaccording to the present invention is used when designing a mobile phonesuch that the mobile phone is curved ergonomically according to theshape of a corresponding region of a human being, it is possible tomaximize space utilization.

Other components of the battery pack and a manufacturing method of thebattery pack are well known in the art to which the present inventionpertains, and therefore, a detailed description thereof will not begiven.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a typical view illustrating a method of manufacturing a curvedbattery cell having a radius of curvature R according to an embodimentof the present invention;

FIG. 2 is a side view illustrating a curved battery cell according toanother embodiment of the present invention;

FIG. 3 is an enlarged view illustrating change of the battery cell at aportion A of FIG. 2 during repetitive charge and discharge of batterycell; and

FIG. 4 is a perspective view illustrating a battery pack including thecurved battery cell according to the embodiment of the presentinvention.

BEST MODE

Now, exemplary embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be noted,however, that the scope of the present invention is not limited by theillustrated embodiments.

FIG. 1 is a typical view illustrating a method of manufacturing a curvedbattery cell according to an embodiment of the present invention.

Referring to FIG. 1, a curve forming apparatus includes an upper jig 210with a convex part 211 having a radius of curvature r and a lower jig220 with a concave part 221 having a radius of curvature r such that thelower jig 220 can be engaged with the upper jig 210. A battery cell 100is configured such that an electrode assembly is provided in a cell casetogether with an electrolyte. The battery cell 100 is mounted in theconcave part 221 of the lower jig 220 in the axial direction thereofsuch that the battery cell 100 can be curved in the axial directionthereof.

When the upper jig 210 is moved downward to the lower jig 220 so as topress the battery cell 100, the battery cell 100 is curved, with theresult that the battery cell 100 has a curved shape corresponding to theshape of the upper jig 210 and the shape of the lower jig 220.

Unlike a conventional case in which the electrode assembly is directlypressed while heat is applied to the electrode assembly, therefore, theelectrode assembly is placed in the cell case, the shape of which ischangeable and the electrolyte is injected into the cell case tomanufacture a battery cell, the manufactured battery cell is initiallycharged and discharged, and then the pressing process, as a postprocess, is carried out with respect to the battery cell. As a result,the deterioration of the electrode assembly is minimized. Furthermore,the electrolyte in the cell case serves as a kind of plasticizer tominimize stress caused due to interface friction between electrodeplates during the execution of the pressing process, and therefore, itis possible to greatly reduce restoration of the battery cell due tosuch stress during charge and discharge of the battery cell.

Meanwhile, the pressing process is preferably carried out in roomtemperature. As needed, on the other hand, a predetermined heattreatment may be further carried out. To this end, a heater (not shown)may be mounted in the upper jig 210 and/or in the lower jig 220.

After the execution of the pressing process, the jigs 210 and 220 areseparated from each other to remove the battery cell 100 from the jigs210 and 220, and then the battery cell 100 is left alone for apredetermined time such that the curved state of the battery cell ispartially restored, and therefore, the battery cell has a radius ofcurvature R. As a result, the stress applied to the battery cell 100through the pressing process is released, and therefore, the curvedshape of the battery cell is stably maintained. A manufactured batterycell 101 has a shape in which the battery cell 101 is curved such thatopposite ends of the battery cell 101 are directed in the samedirection. The radius of curvature R of the battery cell 101 may beequal to or greater than the radius of curvature r of the upper jig 210.

FIG. 2 is a side view typically illustrating a curved battery cellaccording to another embodiment of the present invention.

Referring to FIG. 2, the battery cell 102 is configured such that aradius of curvature R₁ of each end of the battery cell 102 is greaterthan a radius of curvature R₂ of the middle part of the battery cell102.

Consequently, the battery cell 102 has an average radius of curvature R.The radius of curvature R₂ of the middle part of the battery cell 102 isless than the average radius of curvature R, and the radius of curvatureR₁ of each end of the battery cell 102 is greater than the averageradius of curvature R.

The effect obtained by the provision of the above structure can beconfirmed from FIG. 3, which is an enlarged view illustrating a portionA of FIG. 2. FIG. 3 is an enlarged view typically illustrating change ofthe battery cell at a portion A of FIG. 2 during repetitive charge anddischarge of battery cell.

Referring to FIG. 3, electrode plates 110 of an electrode assembly arecurved in almost the same shape as a cell case 120. When the batterycell 102 is repeatedly charged and discharged, however, active materials(not shown) applied to the electrode plates 110 repeatedly expand andcontract, with the result that the electrode plates 110 has a tendencyto be restored to the original shape 110 a thereof. On the other hand,the curved shape of the cell case 120 is maintained. Due to suchrestoration of the electrode plates, therefore, the ends of therespective electrode plates 110 a are pressed by the inside of the cellcase 120. However, the radius of curvature R₁ of each of the electrodeplates 110 a is large, with the result that restored strain isrelatively small as compared with the radius of curvature R.

Specifically, the restored strain is approximately inverselyproportional to the radius of curvature R. Consequently, the restoredstrain is large with respect to electrode plates 130 curved in therelative small radius of curvature R. For this reason, ends of theelectrode plates 130 having the radius of curvature R may be pressed bythe cell case 120, and therefore, the ends of the electrode plates 130penetrate separators (not shown) disposed between the respectiveelectrode plates 130, with the result that a short circuit may occur.

When the battery cell 102 is manufactured such that the battery cell 102has the radius of curvature R throughout the battery cell 102,therefore, it is preferable to manufacture the battery cell 102 suchthat the radius of curvature R₁ of each end of the battery cell 102 isgreater than the radius of curvature R₂ of the middle part of thebattery cell 102, as shown in FIG. 2.

FIG. 4 is a perspective view typically illustrating a battery packincluding the curved battery cell according to the embodiment of thepresent invention.

Referring to FIG. 4, a pack case of a battery pack includes a pack casebody 320 gently curved in the axial direction thereof such that the packcase body 320 has the same shape as the battery cell (see FIG. 2), anupper end cap 310 mounted to the upper end of the pack case body 320,and a lower end cap (not shown) mounted to the lower end of the packcase body 320. The upper end cap 310 is provided with holes 311, throughwhich external input and output terminals protrude outward.

Since the battery pack 300 has a predetermined curved shape, it ispossible to mount the battery pack 300 in electronic devices havingvarious curved designs, such as mobile phones. As a result, the internalspace of each of the curved electronic devices is efficiently used, andtherefore, it is possible to manufacture an electronic device configuredin a structure in which the battery pack is mounted in the electronicdevice in a tight contact manner. Consequently, it is possible todevelop electronic devices having various designs satisfying liking ofconsumers, thereby contributing to diversification of products.

Although the exemplary embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

As is apparent from the above description, the battery cell according tothe present invention is configured such that the electrode assembly ismounted in the changeably cell case in a state in which the electrodeassembly is impregnated with the electrolyte, and the electrode assemblyand the cell case are curved in the same direction on the axial verticalsections thereof in a state in which the opposite ends of the electrodeassembly and the opposite ends of the cell case are directed in the samedirection about the middle part of the electrode assembly and the middlepart of the cell case. Therefore, when the curved battery cell accordingto the present invention is mounted in an electronic device the externalshape of which is curved or in an electronic device configured such thata battery mounting region is curved, the tight contact between thebattery cell and the electronic device is achieved, thereby maximizingspace utilization and thus providing high efficiency. Also, it ispossible to develop electronic devices having various designs satisfyingliking of consumers.

1. A battery cell configured such that an electrode assembly of acathode/separator/anode stack structure is mounted in a changeable cellcase in a state in which the electrode assembly is impregnated with anelectrolyte, wherein the electrode assembly and the cell case are curvedin the same direction on axial vertical sections thereof in a state inwhich opposite ends of the electrode assembly and opposite ends of thecell case are directed in the same direction about a middle part of theelectrode assembly and a middle part of the cell case, and wherein thecurved opposite ends of the electrode assembly and the cell case have aradius of curvature R1, which is greater than a radius of curvature R2of the middle parts of electrode assembly and the cell case.
 2. Thebattery cell according to claim 1, wherein the electrode assembly isconfigured in a stack/folding type structure in which one of stack typebi-cells or full-cells, as unit cells, are sequentially wound in a statein which a long separation sheet is disposed between said one of stacktype bi-cells or full-cells.
 3. The battery cell according to claim 1,wherein the changeable cell case is a pouch-shaped case formed of alaminate sheet including a metal layer and a resin layer.
 4. The batterycell according to claim 3, wherein the battery cell is configured in astructure in which an outer circumference of the pouch-shaped case issealed by thermal welding in a state in which the electrode assembly ismounted in the pouch-shaped case.
 5. The battery cell according to claim1, wherein electrode terminals are provided at at least one of thecurved opposite ends of the electrode assembly.
 6. A manufacturingmethod of a curved battery cell having a radius of curvature R,comprising: (a) mounting an electrode assembly in a changeable batterycell, injecting an electrolyte into the cell case, sealing the batterycell so as to manufacture an upright battery cell, and initiallycharging and discharging the upright battery cell; (b) placing theupright battery cell between upper and lower jigs having a radius ofcurvature r less than the radius of curvature R and moving at least oneof the upper and lower jigs toward the other of the upper and lower jigsto press the upright battery cell; and (c) separating the upper andlower jigs from each other to remove the battery cell from the upper andlower jigs and leaving the battery cell alone for a predetermined timesuch that a curved state of the battery cell is partially restoredresulting in the battery cell having the radius of curvature R.
 7. Themanufacturing method according to claim 6, wherein the step (b) ofpressing the upright battery cell is carried out at a pressure of 150 to500 kgF.
 8. The manufacturing method according to claim 6, wherein thestep of pressing the upright battery cell is carried out at atemperature of 10 to 90° C.
 10. The manufacturing method according toclaim 6, wherein a heater is mounted in at least one of the upper andlower jigs.
 11. The manufacturing method according to claim 6, whereinthe step of pressing the upright battery cell is carried out at a roomtemperature.
 12. A battery pack configured such that a battery cellaccording to claim 1 is mounted in a pack case curved in the same shapeas the battery cell.
 13. The battery pack according to claim 12, whereinthe battery pack is used as a power source for mobile phones.